Would you like a decent - sized cnc router for your garage but you don't have the space or too much money?
No problem! Now you can have one and all you need is a sturdy wall, about £600 for the parts and some tools like:
- Drill press + a set of drill bits + taps (hand drill will not make holes larger than 10mm)
- And other tools that you already have, like some spanners / allen keys, tape measure, engineers square, centre punch, hammer etc.
Now you may be thinking "I don't have a welder - can I just make it out of MDF/plywood?" No!, Forget about MDF and plywood if you want to make a reasonably large and accurate CNC router and plan to keep it in an unheated garage - especially if you live in the UK! Trust me - moisture is your routers worst enemy and it will destroy your wooden machine in one season. Don't ask me how I know this :-)
You can get a brand new gasless welder for just over £100 and I'm sure it will come handy after your'e finished with your build. Alternatively you may know someone who has one. I actually took all the parts to work and asked one of the engineers to weld the pieces up for me while I was on a tea break (not recommended - this is not a job you should rush and I ended up having to make corrections so I just bought a welder to do that).
This is in fact my 3rd build and I'm pretty happy with it now. I'm not saying it's perfect - I'll go over the bad points later so make sure to stick around!
Step 1: Bill of Materials!
These are the major parts that you will need for this build:
£50 breakout board + drivers http://www.ebay.co.uk/itm/CNC-3-axis-Stepper-Motor...
£13 power supply 12v and more than 10A http://www.ebay.co.uk/itm/AC-DC-1A-5A-10A-30A-50A-...
£60 stepper motors http://www.ebay.co.uk/itm/3PCS-1-9Nm-Nema-23-Stepp...
£100 SBR16 fully supported linear rail shaft 16 mm http://www.ebay.co.uk/itm/SBR16-Fully-Supported-Li...
£34 SBR16UU matching linear bearings http://www.ebay.co.uk/itm/Pack-of-4-SBR16UU-16mm-A...
£163 set of 16mm ball screws with machined ends http://www.ebay.co.uk/itm/3-ballscrew-ball-screws-...
£20-ish 5mm mild steel plates http://www.ebay.co.uk/itm/5mm-S355-mild-steel-shee...
£100 mild steel box section profiles http://www.ebay.co.uk/itm/Mild-Steel-Box-Section-/...
£30 Timing belts + pulleys http://www.ebay.co.uk/sch/i.html?_odkw=timing+pull...
You will also need:
A handful of M5 screws, 6 bearings (size dependant on the ballscrews), something for the cutting bed (I currently use some scrap plywood) and some off cuts of Plexiglas.
Step 2: Preparation
This is the Instructable I based my design on: https://www.instructables.com/id/DIY-CNC-Router/
What I liked most about is is that the Y axis rails and the ball screw are all at the same level. This makes the gantry much more rigid and eliminates the pivoting forces on the linear bearings. Also I decided to make the Z axis as short as possible to increase accuracy. Mine has 50 mm travel - more than enough for cutting MDF, plywood etc..
To save me all the cutting I ordered mild steel profiles already cut to the lengths I required. Once It arrived I realised that they were so badly cut, I had to square the ends up by grinding them down to be able to use them. Great thing about this design is that the profiles don't have to be cut to exact lengths - they just have to be welded up square.
Next thing was to drill all the holes and tap them (excluding the ones for ball nuts etc). It needs to be done now, before welding while all the steel pieces can still be placed on the drill press. Lots of measuring and centre punching.
I used 60x40mm profiles for the frame, 40x40 and 25x50 mm for the gantry. Also a couple of small 40x40 offcuts for ball nut mounts for X and Z axis.
On the picture above you can see that I added a piece of metal profile to my bearing mount. That's because my ball screw was too short and I didn't want to cut the linear rails to match the size.
Step 3: The Gantry and the Frame
Gantry was the first thing that was welded together. Take your time with this to make sure everything is square.
Once the gantry is in one piece, I added the linear bearings and partially welded up the frame. Only weld up the front and back and one side where the Y axis will be, so that the frame forms a C shape. Put everything on a flat surface and attach the gantry with the bearings to the Y axis rails. Attach the other side of the frame with the linear rail and bearings. Slide the gantry over to the front - now you know exactly where to weld the remaining part of the frame. Next slide the gantry over to the back and weld the other side of the Y axis. When done, the gantry should slide smoothly without binding.
Step 4: The Z Axis
The Z axis is pretty standard design apart of the way that the screw is mounted. On photo 1 you can see the Z screw and the bearing mount made from plexiglas. The other side of the screw is supported by a bearing and being held by the top plate to which the motor is mounted. I must admit - I was pretty happy with the look of this - it looks heavy duty. I stuck to 1:1 gearing ratio on this axis. You could probably get away with a smaller motor too If you can be bothered to try :-)
Step 5: Assembly Tips and Tricks
You may have noticed that I never mentioned any bearing mounts, ball nuts mounts or motor standoffs in the BOM. Thanks to this design you can save a few ££'s (or $$'s) by not having to buy these.
The pictures above show how I mounted the ball screws for all of the axes. I unscrewed the motor plate to show how the bearing sits in the frame (it's not a tight fit as I didn't have a drill bit this size). For Drilling out big holes I used step drills - that's why you really need a drill press. What is critical is that the ball screw cannot move along the axis it is driving. I achieved this by placing the bearing in a Plexiglas holder and made tiny adjustments by sanding it down until the ball screw turned freely but without any play.
You may have noticed that in BOM I linked up a listing for one linear rail, 1000 mm long. I found it's cheaper to buy 4 Long rails and cut two of them to use for the Z axis.
Also, I had to use pulleys with gearing ratio of around 3:1 as my ball screws have 5mm pitch, which resulted in low speeds. 5mm pitch means that the nut will move by 5mm every turn. I have linked up ball screws with a 10mm pitch, so you will ideally need a 2:1 ratio on the pulleys.
I added some rubber lining under the motors and Y axis ball nut to help dampen the vibration and the whole thing is really silent despite being made out of metal.
Now for the spindle bracket. I made my own out of 2 layers of 12 mm acrylic glued together. You can buy a ready made one but I couldn't find one with the right diameter.
Step 6: Put It on the Wall
I made a sliding mechanism in which the whole machine can slide up and down (picture 3). Because the whole machine is quite heavy, I added a pulley on the ceiling and attached a rope to the back of the router. This helps me lift it up and unfold it gently. This saves a lot of room in my garage when I'm not using the router.
Step 7: Things I'd Upgrade or Do Differently
If I was building this machine again, I'd do all the welding myself and take my time with it. Some things are not super square which is not ideal but I still managed to get everything running smoothly.
First on the list to be upgraded is the cutting bed. As I mentioned in the beginning, I don't want any part of this machine to absorb moisture and expand or shrink. I planed the cutting bed earlier in the summer and now it's all bumpy again. I'm considering replacing that with a 20 mm sheet of HDPE or ideally a 19mm tufnol sheet.
Here is a link to my thread regarding this, if your'e interested: http://www.mycncuk.com/threads/10448-Waterproof-CN...
Next up for upgrade will be the spindle. I'm currently using a hand router which is less than perfect for CNC. The major problem with it is that the motor inside is only attached to the housing on the bottom, where the bearing is. This causes some deflection when cutting. At least it has adjustable RPM and a tachometer for constant cutting speed.
Recently I stumbled upon a DIY brushless spindle, using a motor for an RC car or drone: http://www.mycncuk.com/threads/3793-Diy-brushless-...
So this is what I'm considering unless you help me win one of the second prizes in the CNC contest - that would be much appreciated :-)
Another upgrade would be to add another ball screw for the Y axis - to have one at either side. This would make the gantry much more rigid, but so far I have not had a need for this - It's good as it is.
Also some cross Bracing would make the frame more sturdy. A cheap, simple and effective upgrade - maybe in near future.
That would be it for now, I hope some of this makes some sense, please comment, like and subscribe!
Thanks for your time and I hope you like this Instructable!